This may be a bit hair-raising to achieve. The old /Users/username/Library/StickiesDatabase digest file is no longer used by macOS after macOS Catalina where the digest entries are split out as individual RTFD (rich text folders) containing the Stickies data.
On your Mac, press shift+cmd+G (go to folder) and enter the following followed by a return:
~/Library/Containers/com.apple.Stickies/Data/Library/Stickies
That will open a new Finder window on the folder containing your Stickies whose format is stored in Rich Text Folders (.rtfd). You can single-click on these individual .rtfd Stickies and press the space bar to view the contents in Quick Look.
With that folder still open, launch the /Applications/Time Machine application and it should open to the same location as your current Finder Window — on the Time Machine drive. You can also use Quick Look here to view the Stickies' contents. Use the arrow keys to go back in time and when you see the Stickie(s) that you want, select them and click Restore. They will be put back into your local drive location and you should see them in your open Finder Window on that Stickies location.
